Tuesday, August 16, 2011

Dave Gibson on Birding: The Tale of the Veery

Summer has flown. Bird song no longer greets our sunrise. Many Adirondack migratory songbirds are starting to fly to their wintering grounds in Central and South America and the Caribbean islands this month. I take account of one very familiar bird I really missed this summer. Since we moved to Saratoga County in 1984, the flute-like, descending song of the male Veery ( Ve-urr, Ve-urr, Ve-urr) penetrated from our woodlands, beginning in late May and lasting well through the summer. The bird bred and raised young here for at least 25 years, and probably for centuries before that.

Veery, one of our familiar upstate thrushes, was a constant in our summer lives until this year when I only began to hear Veery in our woods in mid- July, long after this species usually nests. Its immediate habitat hadn’t changed. With this 50-acre patch of forest habitat more or less unchanged, I conjecture there were simply fewer breeding Veery in the area to fill its favorable habitat, and a non-breeding adult came to these woods late in their season.

The Second Atlas of Breeding Birds in New York State (McGowan and Corwin, eds., Cornell University, 2008) states that Veery (Catharus fuscescens) generally nests in damp, deciduous forests with dense undergrowth. This description fits our woods perfectly. It also says that from 1966 to 2005 Veery populations have declined range wide at a significant rate of -1.5 percent per year. For the years 1985-2005, the declines are even greater.

I picked up a copy of Silence of the Songbirds by Bridget Stutchbury (Walker and Co., 2007), and learned a lot more about my Veery. The author writes:

“Until recently, the veery was thought to have a large wintering range that coincided nicely with the biggest tropical forest wilderness remaining in the world, the western Amazon. Since it was one of the few migrants to enjoy a largely intact wintering habitat, the cause of its steep population decline must lie in the breeding grounds or somewhere en route. A careful look at museum specimens that were collected in South America showed that in fact all the veery collected during the winter were from the woodlands of south-central Brazil. The specimens from the western Amazon and northern South America were birds that were passing through on migration in early fall or early spring. The true size of the veery’s winter range is as little as 10 percent of the earlier estimate and is much farther o the south, in a heavily populated and agricultural region of southern Brazil.”

Many of us who grew up with Rachel Carson’s 1962 classic Silent Spring have been waiting for a kind of sequel that reflects the realities of the unraveling of the earth’s life support systems that we know is happening and to which birds are exquisitely sensitive. In its global scope, scientific rigor and message that humans hold in their hands the future of a vast migratory birdlife, Silence of the Songbirds is a most worthy candidate as a sequel.

The losses of migratory birds from the widespread introduction of pesticides after World War II documented by Carson have been completely eclipsed by the rapid declines across dozens of bird species due to a combination of massive tropical deforestation and pesticide use, and rapid changes in North American and boreal forests due to habitat fragmentation, introduction of new bird and nest predators and of thousands of new radio, television, wind and cellular phone towers which kill birds in migration. Stutchbury not only explains and catalogues these lethal and sublethal hazards, but reminds us what we can do about them.

A bird ecologist who has closely studied bird natural history in the tropics of South and Central America, United States and Canada, in her book Stutchbury shows her intimacy with mountains of new data about how and where particular bird species migrate, live out of their lives, socialize and sort out habitats on their wintering grounds and breeding grounds of North America. She chronicles the miracles of the communication and social behavior of, for example, the Hooded and Kentucky Warbler on their North American breeding grounds as well as her study sites in Central America. While the Kentucky Warbler’s southerly breeding range makes it unfamiliar to many of us in upstate New York, the flutelike song of our beloved Wood Thrush is no longer heard in many upstate New York woodlands because it faces the same massive change in wintering habitat. As she writes:

“Kentucky warbles and wood thrush are both forest birds that have declined dramatically in the past few decades. Their entire wintering range in Central America has undergone extreme deforestation during this same period. Both species are territorial, so they cannot simply crowd into remaining forest and share what little habitat is left.”

Stutchbury clearly communicates for the lay reader the complexities of how “our songbirds” are forced to overwinter in small, scrubby patches of the former vast forests of South and Central America, where she estimates 750 million acres of tropical forests were lost during the 20th century for lumber, coffee, cacao and other plantations. While birds may survive in these scrub patches, they do not thrive due to their level of stress. We all relate to heightened hormonal levels released under stressful situations, like our daily work commutes in an automobile. The author cites heightened stress hormones in overwintering birds living in lousy habitats, “chronically short of food, living under the constant threat of predation, or frequently chased and harassed by other birds.” These birds tend to be underweight as they begin their long northward migration and less successful as breeders if they survive their long journey.

Throughout, Stutchbury reminds us that we can make a difference. She devotes an entire chapter to coffee ecology, meaning the stark differences in habitat between sun and shade-grown coffee and the big effect our coffee drinking choices can make. Shade-grown coffee trees mimic to some degree tropical forests in the degree of shelter and food they offer to a wide variety of bird species. Massive replacement of more traditional shade-grown coffee plantations to full sun-grown coffee may have resulted in some of the dramatic declines of songbird populations seen during the 1990s. Stutchbury makes a compelling case that buying shade-grown coffee is, truly, investing in habitats in which overwintering birds can not just survive, but thrive.

In this very readable, dramatic story of the gauntlet which our beloved thrushes, warblers, tanagers, vireos and other songbirds of forests and fields run, Stutchbury provides much food for thought about the impact our life choices have on bird survival. She also offers much for the serious student of birds as well.

The final chapter focuses on why birds tend to prefer larger, unfragmented forests to smaller forest patches. For decades, it was thought that deep forest birds avoided patches because of their many edges. Forest birds avoided forest edges largely due to losses of eggs from edge-effect predators.

In addition to these predatory impacts, Stutchbury explains another reason. She writes that it is their social behavior that drives so many forest birds to avoid forest fragments. The migratory songbirds we welcome back each spring require tightly packed bird neighborhoods of their own species because about half of migratory songbird females mate with more than one male. Promiscuity in songbirds, it turns out, is not antisocial but part of their North American survival strategy. Larger forests provide the critical and crowded habitats for bird society to play itself out during the brief breeding months before they turn, once again, to the dangerous migratory routes and an uncertain welcome and lengthy stay in the southern hemisphere.

Silence of the Songbirds will heighten awareness of birds and their critical ecological role in tree seed distribution and insect predation. Our forests depend on birds, and visa-versa. Their fate and our fate are intertwined, and very much in human hands.

Photos: Veery, courtesy of US Fish and Wildlife Service, photo by Dan Sudia; and good Veery breeding habitat occupied for the past 25 years, until this summer.

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Dave Gibson, who writes about issues of wilderness, wild lands, public policy, and more, has been involved in Adirondack conservation for over 30 years as executive director of the Association for the Protection of the Adirondacks, executive director of Protect the Adirondacks and currently as managing partner with Adirondack Wild: Friends of the Forest PreserveDuring Dave's tenure at the Association, the organization completed the Center for the Forest Preserve including the Adirondack Research Library at Paul Schaefer’s home. The library has the finest Adirondack collection outside the Blue Line, specializing in Adirondack conservation and recreation history. Currently, Dave is managing partner in the nonprofit organization launched in 2010, Adirondack Wild: Friends of the Forest Preserve.

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6 Responses

  1. mountainlady says:
  2. Dave Gibson says:
  3. Chris says:

    Recent research done with Veeries breeding in White Clay Creek State Park (in the Piedmont region of Delaware) has revealed that the Veery’s winter range is a bit more complicated than previously thought. Birds in Delaware were fitted with tiny Geolocators that stored data pertaining to day length and angle of the sun during the birds’ migration from Delaware to South America and back again. All of the birds did indeed head first to southern Brazil and spent a good part of the winter there. But when the rivers started to rise and flood the forests, inundating the habitat the Veery’s were utilizing, usually by early February Veeries migrated a second time to nothern Brazil and southern Venezuela where they stayed until beginning their return migration to Delaware in mid to late April. This work was done by Dr. Christopher Heckscher of Delaware State University. Read the article in the Auk Vol. 128 No. 3, July 2011.

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